The replies from Christopher Frye and Jon are the classic textbook answers. If you want to understand traditional fairy tales, or nineteenth-century literature, for example, these answers are correct and helpful. If a character in a Jane Austen novel said 'I shall go', this was a neutral statement about the future. But if the same character wanted, for example, to show stubborn determination, she'd say "I will go". Let's imagine that the young girl's parents have forbidden her to go to a dance, she might argue with them, stamp her pretty foot, and exclaim "I will go" before storming out of the room. However, this does not apply to modern English. These modal verbs are not used in this way any more. This distinction was already outdated 50 years ago, and it no longer applies. So how do we use these words nowadays? As the answers above show, the vast majority of native speakers have absolutely no idea about the difference between the difference between 'will' and 'shall'. Especially in the US, there is a mistaken belief that 'shall' is nothing more than a pretentious, formal or - worse still - 'British' alternative to 'will' that can be used at random (with any grammatical subject) in official documents and fancy speech. Here's the truth. In modern English, it's possible to use either 'shall' or 'will' with the same meaning in first-person statements: 'I shall be there' and 'I will be there' mean the same. Likewise 'I won't go' and 'I shan't go'. However, this flexibility does not apply to questions. In first-person question forms, for offers and suggestions, you have to use a 'sh...' modal, either 'Shall I go?' or 'Should I go?'. You can't use 'will' for these types of first-person questions. But do you need to use 'shall'? No, you don't. Most native speakers never say 'shall'. 'Will' and 'shall' are certainly not interchangeable, but you can always replace the first-person 'shall' with 'will' or 'll in statements, or 'Should....?' in questions.

Shall is used mainly in first person form but can be used in the second and third-person forms if it's indicating a strong determination. It's also more polite than "will" but it is less commonly used. Will is used in the second and third-person forms but is used in the first-person when indicated a strong determination.

Christopher is right. The example I always think of is "Cinderella, you shall go to the ball!" This is the Fairy Godmother effectively making a promise to Cinderella (perhaps you know the story). An onlooker might then remark "Well Cinderella, it looks as if you will go to the ball after all. It's lucky your Fairy Godmother turned up." This is simply a statement of fact: no promise is being made. I disagree with La Liseuse - this distinction is still in use, although it is less obvious because of the contractions I'll & we'll, and is not as universal as it used to be (as she says, in negatives it is more common to say I "won't" than I "shan't"). But in questions, unless you're Scottish you always say "shall I?" and "shall we?" The only time you would say "will I be going to Paris?" is if the power to make it happen is in someone else's hands, such as your boss at work - in other words, you're asking for a promise. (The same distinction, by the way, doesn't apply to "would" and "should". You can use either for any person in all circumstances. "Would I...?" and "should I...?" are both fine and mean different things.)

Thanks for your supplementary explanation, Ashton.

Shall is from “Old English” or “Poetic English” used in the past. For example I can think of a specific type of Bible written in this way. You can search it online. But “shall” and “will” are the same in terms of meaning - intent to complete or do something It’s the future tense of going to. In this period of time most people are just <<going to>> use ”going to” because it’s easier and fairly simple. But when you’re talking about years 5 - 10 - or 20 years into the future; many people use statements using “will” but again it makes no difference if you use “going to” because it is a statement of intent. I hope 🤞🏾 this helps.